Probiotic <i>Propionibacterium freudenreichii</i> requires SlpB protein to mitigate mucositis induced by chemotherapy

Abstract

<i>Propionibacterium freudenreichii</i> CIRM-BIA 129 (<i>P. freudenreichii</i> wild type, WT) is a probiotic bacterium, which exerts immunomodulatory effects. This strain possesses extractable surface proteins, including SlpB, which are involved in anti-inflammatory effect and in adhesion to epithelial cells. We decided to investigate the impact of <i>slpB</i> gene mutation on immunomodulation <i>in vitro</i> and <i>in vivo</i>. In an <i>in vitro</i> assay, <i>P. freudenreichii</i> WT reduced expression of IL-8 (p<0.0001) and TNF-α (p<0.0001) cytokines in LPS-stimulated HT-29 cells. <i>P. freudenreichii</i> Δ<i>slpB</i>, lacking the SlpB protein, failed to do so. Subsequently, both strains were investigated <i>in vivo</i> in a 5-FU-induced mucositis mice model. Mucositis is a common side effect of cytotoxic chemotherapy with 5-FU, characterized by mucosal injury, inflammation, diarrhea, and weight loss. The WT strain prevented weight loss, reduced inflammation and consequently histopathological scores. Furthermore, it regulated key markers, including Claudin-1 <i>(cld1</i>, p<0.0005) and IL-17a (<i>Il17a</i>, p<0.0001) genes, as well as IL-12 (p<0.0001) and IL-1β (p<0.0429) cytokines levels. Mutant strain displayed opposite regulatory effect on <i>cld1</i> expression and on IL-12 levels. This work emphasizes the importance of SlpB in <i>P. freudenreichii</i> ability to reduce mucositis inflammation. It opens perspectives for the development of probiotic products to decrease side effects of chemotherapy using GRAS bacteria with immunomodulatory surface protein properties.